@mixin theme($theme: DarkGray) {
    background: $theme;
    box-shadow: 0 0 1px rgba($theme, 0.25);
    color: #fff;
}

.info {
    @include theme;
}

.alert {
    @include theme($theme: DarkRed);
}

.success {
    @include theme($theme: DarkGreen);
}
